Officers repeatedly asked him to put down the weapon but he refused as he told them, "Don't come near me."

Mr Willis told the court it was then the shutters were closed to protect people working behind them.

He told the court Collier was then restrained adding: "It is fortunate there were no members of the public present because there was real and potential danger for the officers."

As Recorder Abigal Nixon jailed Collier for a year, she told him: "It is clear to me that had anyone challenged you in the state you were in they could have been hurt or worse.

"It is good fortune that no-one was hurt. The courts must punish those who carry knives in public - particularly when they are in drink."

She said Collier, of Broad Street, had been allowed to keep his freedom by courts in the past and concluded: "You have had your chances and you chose to disregard them."

The court heard there were no protective screens at the entrance to the building and the actions of Collier left one staff member "frightened and shocked" when the knife was produced.

Gurdeep Garcha, for Collier, who admitted possessing a bladed article, said his client had a drink problem and went on: "He has expressed a desire to address his troubles."

He said there was clear evidence of contrition and remorse from Collier who, he maintained, had made a "significant improvement" in his bid to put his life back on track but, at the time of the offence, he "could not cope."